1. Field of the Invention
The invention relates to an aerodynamic element for attachment to a wing, or a wing with a primary wing. At least one such additional aerodynamic element can also be utilized. A computer with an actuator-activation module is also provided, as well as a computer program for implementation in a computer with an actuator-activation module. A method for influencing command signals for an actuator system is also provided, as well as combinations of such a computer with an actuator-activation module, a wing and at least one actuator for purposes of destabilizing wake eddy systems, which can take place utilizing, in particular, multi-part, active flow flaps.
2. Discussion of Background Information
Aircraft produce wake eddy systems, so-called eddy trails, owing to pressure differences between the upper side of the wing with a low pressure level and the lower side of the wing with a high pressure level. As a result, air flows from the lower side of the wing to its upper side at the ends of the wing, generating an eddy (wing tip or edge eddy). In addition, fluid layers at the rear edge of the airfoil coming from the upper and lower side flow past each other in varying directions, giving rise to a free shearing layer, which is connected with the respective edge eddy in the spanwise direction. Self induction causes this free shearing layer to unfurl itself along with the respective edge eddy into two counter-rotating individual eddies, the cores of which can reach peak speeds of up to 360 km/h, depending on flight conditions or aircraft size.
The wake eddy system remains detectable up to several hundred spans downstream from the aircraft, before dissipating because of instability mechanisms and/or atmospheric effects. As a result, the eddy trail in large aircraft can last for several minutes and reach up to 30 km in length, for example. Additional high-energy eddies arise when the aircraft is in high-lift configurations, i.e., especially during takeoff and landing, with slat and trailing edge flaps deployed. In particular, the outer lateral flap edges develop additional eddies, the intensity of which can exceed that of the wing tip eddies.
Depending on the position in the eddy field, a subsequent aircraft flying into an eddy trail is exposed to an upwind field, a downwind field (loss of lift) or an induced rolling moment associated with more or less intensive speed fluctuations. This can lead to serious consequences, especially for an aircraft smaller than the aircraft flying ahead of it. These are manifested in an elevated structural dynamic load, ultimately resulting in a loss of stable attitude, for example if the planned rolling moment is no longer sufficient to compensate for the rolling moment induced by the eddy trail.
Since the strength of the two individual eddies remaining after the unfurling process is proportional to the overall circulation, and hence to the lift countering the weight of the aircraft, the safety distances between two consecutive aircraft are geared toward their maximum takeoff weight (takeoff mass).
In order to diminish the potential danger to subsequent aircraft, it is known from general prior art to influence the spatial eddy strength distribution in the wake, thereby reducing the induced rolling moment or utilizing and actuating inherent instability mechanisms in the eddy systems to make the eddy trail decay more quickly.
For example, U.S. Pat. No. 6,082,679 B1 discloses a method for selecting control parameters of an active control system for the early destruction of eddy trails by moving wing control surfaces such as ailerons and spoilers. In this solution, the near-field turbulence of the wing is determined, and an amplification mechanism is selected to change the eddy trial. Amplitudes and wavelengths of the applied eddy disruptions are then determined, and eddy wake development is simulated, while the eddy position is determined as a function of control surface displacements.
The disadvantage to such systems is that they cause an overlapping of the actual functionality, e.g., roll control, due to the use of control surfaces already present on the aircraft, like ailerons and spoilers. This multifunctionality results in a considerable extra outlay with respect to aeroelastic analysis and the flight control system.